Custom button event not firing

Question

I have modified pca10040.h as 
 #define BUTTONS_NUMBER 5

#define BUTTON_START 13
#define BUTTON_1 13
#define BUTTON_2 14
#define BUTTON_3 15
#define BUTTON_4 16
#define BUTTON_5 17
#define BUTTON_STOP 17
#define BUTTON_PULL NRF_GPIO_PIN_PULLUP

#define BUTTONS_ACTIVE_STATE 0

#define BUTTONS_LIST { BUTTON_1, BUTTON_2, BUTTON_3, BUTTON_4, BUTTON_5 }

#define BSP_BUTTON_0 BUTTON_1
#define BSP_BUTTON_1 BUTTON_2
#define BSP_BUTTON_2 BUTTON_3
#define BSP_BUTTON_3 BUTTON_4
#define BSP_BUTTON_4 BUTTON_5
 
 Modified sdk_config.h 
 #ifndef GPIOTE_CONFIG_NUM_OF_LOW_POWER_EVENTS
#define GPIOTE_CONFIG_NUM_OF_LOW_POWER_EVENTS 5
#endif
 
 Add a button on breadboard one leg on gnd one on pin 17 
 On press i was expecting bsp_event_handler to get fired with event BSP_EVENT_KEY_4. But it did not. 
 So i added custom code to assign an event 
 err_code = bsp_event_to_button_action_assign(4,
 BSP_BUTTON_ACTION_PUSH,
 BSP_EVENT_KEY_4);
 
err_code = bsp_event_to_button_action_assign(4,
 BSP_BUTTON_ACTION_RELEASE,
 BSP_EVENT_KEY_4);
 
err_code = bsp_event_to_button_action_assign(4,
 BSP_BUTTON_ACTION_LONG_PUSH,
 BSP_EVENT_KEY_4);
 
 But it still not firing. But if i assign new event to any of pca10040 boards button it works. But just does not work for custom button. 
 Assigning to pca10040 board button number 4 
 err_code = bsp_event_to_button_action_assign(3,
 BSP_BUTTON_ACTION_RELEASE,
 BSP_EVENT_KEY_5);
 
 Also if i connect pin 16 (pca10040 button 4) to custom button on breadboard then also it works. 
 So i tried all combinations to make sure connections are right but my custom button code does not work.
What is wrong with my code for custom button?